It is well known in the art to provide vehicles with on board systems for achieving inflating and/or deflating of vehicle tires and/or the checking of the pressure of air in the vehicle tires. The ability to selectively increase or decrease tire pressure is desirable in connection with optimizing operation of the vehicle under variable and changing conditions including, for example, weather, vehicle load, terrain and vehicle speed. Another advantage of such systems is their ability to isolate air under pressure in each vehicle tire from the remainder of the system so that any problem, such as a leak, encountered in connection with one tire does not affect the air pressure in the other vehicle tires. Generally, most of the tire pressure control systems use a tire isolating valve interposed between the tire and the tire pressure control system and the sealing arrangement effected by the isolating valve is not severely strained because the isolating valve is not subjected to system air pressure other than when the system is operated to achieve inflation, deflation or pressure checking.
In my parent patent, an electronic-pneumatic control system is disclosed in combination with a unique tire isolating valve of the poppet type which, when manually actuated, provides a fully automated, highly accurate system for controlling the inflating, deflating and pressure checking of the vehicle's tires. One of the features of my parent patent is to conceptually utilize system pressure to initialize whatever tire pressure function the system is being instructed to do and, once initialized, utilize an orificing arrangement to sense the tire pressure which in turn controls the system pressure and valving to achieve whatever tire pressure function the system is being asked to perform. For example, when the system in my parent patent is manually placed in a discharge or tire deflation mode, system pressure is initially used to open the isolating valve. The tire pressure is then essentially discharged to atmosphere through an orifice until a predetermined lower tire pressure is accurately sensed. At that point in time, the valving system is again actuated to instantaneously close the tire isolating valve by rapidly dumping the manifold pressure to atmosphere thus bypassing the orifice sensing arrangement.
In practice, the valving and the system disclosed in my parent patent rapidly deflates the system in the tire deflation mode and satisfies most vehicular applications requiring tire deflation. However, there are applications, for example in military transport vehicles, where it is desired to have almost instantaneous deflation. This can occur when the vehicle encounters mud, water or sand and must keep its speed as high as possible. In such instances, tire deflation systems which exhaust the tire air through the system manifold or the system manifold lines will inherently produce a delay in the tire deflation mode. One can appreciate the significance of the problem by visualizing a six-wheel vehicle deflating all of the air from its six tires through one manifold line. Further compounding the problem is a definite trend over the past several years to increase tire size on such vehicle. Obviously this requires that a larger fluid mass be discharged to achieve the same deflation pressure of older vehicles using smaller tires.
Quick dump valves are well known in the general art and the use of a quick dump valve to achieve rapid deflation of a tire in a vehicular tire pressure control system has been recognized in the prior art. A typical approach is disclosed in U.S. Pat. No. 2,989,999 to Holbrook, incorporated by reference herein. In Holbrook, a quick dump valve is used at each tire to directly discharge the fluid in the tire to atmosphere upon command by air (which is at a higher pressure than the system pressure) being ported to the dump valve. The quick dump valve is spring biased and whenever the tire pressure drops below the compressed force of the spring, the valve shuts off to stop further tire deflation. This is workable so long as only one lower, tire deflation value is required and so long as the spring rate can be accurately correlated to the pressure sensed in that particular tire to which the valve is attached. Today, several deflation pressures are typically required with little pressure variance permitted between the vehicle's tires.